(1) Field of the Invention
The present invention relates generally to cable towing systems, and more particularly to a towed array handling system having a tow point located in the mid ships area of a submerged vessel.
(2) Description of the Prior Art
Current thin line towed arrays are deployed and retrieved from a submarine through a tow point located at the tip of the horizontal stabilizer as shown in U.S. Pat. No. 5,119,751 to Wood. That location is not only the best from the standpoint of the affects on ship maneuvering, but it is the only location which avoids entanglement and severing of the array in the ship's screw on submarines not equipped with a shrouded screw. The towed array handling system on submarines is located either in the aft ballast tank or in a mid ships area. From either of these positions, the towed array must be ducted through a long, curved guide tube extending from the handling equipment to the aft tow point. Even though equipped with rollers to reduce friction, the guide tube still increases the free stream drag on the array, thus necessitating the use of a dual capstan type traction device to reduce the array tension to a level considered safe for wrapping onto a storage reel. Current traction devices are designed with three foot diameter sheaves. Repeated cycling of the array over the guide tube rollers, in addition to repeated wrapping around the three foot diameter sheaves at elevated tensions, degrades the towed array structure and reduces the life of the towed array.
Future submarine sonar capabilities will demand either multiple, long, single line arrays or multi line arrays in which several shorter arrays are towed by a single tow cable. Furthermore, the arrays may be towed from two separate tow points. The aft ballast tanks are not expected to offer space for either a second handling system the size of the current single line handling system or a handling system capable of accommodating a multi line array. Tests performed on multi line arrays, especially those equipped with lateral force devices, have demonstrated that these arrays cannot be deployed or retrieved through a guide tube having multiple three dimensional curves; nor can the multiple arrays be detensioned on dual capstan type traction devices. The various studies and tests of handling system characteristics have determined that the following characteristics are necessary for handling multi line arrays: (1) A large diameter, narrow faced reel must be used for storage or the array and to apply the primary inhaul force for both the single line arrays and the multi line arrays; (2) The arrays must be ducted from the storage reel to the tow point via a guide duct having the minimum number of bends, the planes of which are coincident with the plane of the storage reel; and (3) A simple transfer device located in one of the bends must be used to assist the initial phase of deployment and to eliminate friction in the bend at retrieval.